/*
 * Copyright [2013-2021], Alibaba Group Holding Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.alibaba.polardbx.optimizer.core.planner;

import org.apache.calcite.rel.RelNode;

import com.alibaba.polardbx.optimizer.core.CursorMeta;
import org.apache.calcite.sql.SqlNode;

/**
 * For sql unsupported to cache, use this placeHolder to cache. DO NOT throw
 * exception at cache.load, for multi threads, it DOESN'T work correctly.
 * <ref>https://github.com/google/guava/wiki/CachesExplained#interruption</ref>
 *
 * @author lingce.ldm 2018-06-22 19:29
 */
public class PlaceHolderExecutionPlan extends ExecutionPlan {

    public static final PlaceHolderExecutionPlan INSTANCE = new PlaceHolderExecutionPlan(null, null, null);

    private PlaceHolderExecutionPlan(SqlNode ast, RelNode plan, CursorMeta columnMeta) {
        super(ast, plan, columnMeta);
    }
}
